dmesg

Messages that are produced by the kernel are placed in a ring buffer which has a default size of 16392 bytes. This buffer is available from userspace via /proc/kmsg. Messages are categorized into levels which are also used to decide which are printed to the console.

Define

Level

Description

KERN_EMERG

-

System is unusable

KERN_ALERT

1

Action must be taken immediately

KERN_CRIT

2

Critical conditions

KERN_ERR

3

Error conditions

KERN_WARNING

4

Warning conditions

KERN_NOTICE

5

Normal but significant condition

KERN_INFO

6

Informational

KERN_DEBUG

7

Debug-level messages

dmesg allows printing and controlling the ring buffer:

Show content:dmesg

Console verbosity level:dmesg -n LEVEL

Ring buffer size:dmesg -s SIZE

Clear ring buffer:dmesg -c

Feedback is always welcome! If you'd like to get in touch with me concerning the contents of this article, please use Twitter.